sched/wait: Introduce prepare_to_wait_event()

Add the new helper, prepare_to_wait_event() which should only be used
by ___wait_event().

prepare_to_wait_event() returns -ERESTARTSYS if signal_pending_state()
is true, otherwise it does prepare_to_wait/exclusive.  This allows to
uninline the signal-pending checks in wait_event*() macros.

Also, it can initialize wait->private/func. We do not care if they were
already initialized, the values are the same. This also shaves a couple
of insns from the inlined code.

This obviously makes prepare_*() path a little bit slower, but we are
likely going to sleep anyway, so I think it makes sense to shrink .text:

               text    data      bss      dec     hex  filename
            ===================================================
   before:  5126092 2959248 10117120 18202460 115bf5c   vmlinux
    after:  5124618 2955152 10117120 18196890 115a99a   vmlinux

on my build.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131007161824.GA29757@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 38 insertions, 10 deletions

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 04c0260bda8f..ec099b03e11b 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -187,27 +187,30 @@ wait_queue_head_t *bit_waitqueue(void *, int);
         __cond || !__ret;                                               \
 })
 
-#define ___wait_signal_pending(state)                                   \
-        ((state == TASK_INTERRUPTIBLE && signal_pending(current)) ||    \
-         (state == TASK_KILLABLE && fatal_signal_pending(current)))
+#define ___wait_is_interruptible(state)                                 \
+        (!__builtin_constant_p(state) ||                                \
+                state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE)  \
 
 #define ___wait_event(wq, condition, state, exclusive, ret, cmd)        \
 ({                                                                      \
         __label__ __out;                                                \
-        DEFINE_WAIT(__wait);                                            \
+        wait_queue_t __wait;                                            \
         long __ret = ret;                                               \
                                                                         \
+        INIT_LIST_HEAD(&__wait.task_list);                              \
+        if (exclusive)                                                  \
+                __wait.flags = WQ_FLAG_EXCLUSIVE;                       \
+        else                                                            \
+                __wait.flags = 0;                                       \
+                                                                        \
         for (;;) {                                                      \
-                if (exclusive)                                          \
-                        prepare_to_wait_exclusive(&wq, &__wait, state); \
-                else                                                    \
-                        prepare_to_wait(&wq, &__wait, state);           \
+                long __int = prepare_to_wait_event(&wq, &__wait, state);\
                                                                         \
                 if (condition)                                          \
                         break;                                          \
                                                                         \
-                if (___wait_signal_pending(state)) {                    \
-                        __ret = -ERESTARTSYS;                           \
+                if (___wait_is_interruptible(state) && __int) {         \
+                        __ret = __int;                                  \
                         if (exclusive) {                                \
                                 abort_exclusive_wait(&wq, &__wait,      \
                                                      state, NULL);      \
@@ -791,6 +794,7 @@ extern long interruptible_sleep_on_timeout(wait_queue_head_t *q, signed long tim
  */
 void prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state);
 void prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state);
+long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state);
 void finish_wait(wait_queue_head_t *q, wait_queue_t *wait);
 void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, unsigned int mode, void *key);
 int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key);
diff --git a/kernel/wait.c b/kernel/wait.c
index d550920e040c..de21c6305a44 100644
--- a/kernel/wait.c
+++ b/kernel/wait.c
@@ -92,6 +92,30 @@ prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state)
 }
 EXPORT_SYMBOL(prepare_to_wait_exclusive);
 
+long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state)
+{
+        unsigned long flags;
+
+        if (signal_pending_state(state, current))
+                return -ERESTARTSYS;
+
+        wait->private = current;
+        wait->func = autoremove_wake_function;
+
+        spin_lock_irqsave(&q->lock, flags);
+        if (list_empty(&wait->task_list)) {
+                if (wait->flags & WQ_FLAG_EXCLUSIVE)
+                        __add_wait_queue_tail(q, wait);
+                else
+                        __add_wait_queue(q, wait);
+        }
+        set_current_state(state);
+        spin_unlock_irqrestore(&q->lock, flags);
+
+        return 0;
+}
+EXPORT_SYMBOL(prepare_to_wait_event);
+
 /**
  * finish_wait - clean up after waiting in a queue
  * @q: waitqueue waited on